I have a question regarding selection of cells by treatment with puromycin. If the majority of cells apoptose, won't the medium become quickly toxic as the cell fragments degrade and spill? I figure I could overcome this by repeatedly replacing the medium but how often? I imagine this even more of nuisance if your cells are in suspension and need to be centrifuged every time.

-seanspotatobusiness-

Quickly is subjective - changing medium every 24-48 hours should be OK, and with puro the majority of susceptible cells will be dead within a few days. The burden of dying cells will depend on your transfection efficiency, so somewhere about 70-50% of the vessel will die (i.e. 30-50% transfection efficiency), for most vessels this isn't a huge number of cells given that they should start at around 70% confluent.